1. Field of the Invention
The present invention pertains to a resistor for controlling a fan motor rotation speed for use in an air conditioner.
2. Description of the Related Art
Conventional automotive vehicles are necessarily provided with a cooler or a heater for air-conditioning purpose. The cold or hot air generated from the cooler or heater is forcibly supplied to a passenger room of the vehicle under the action of a motor-driven fan.
Such an air conditioning system is constructed such that a driver can regulate the intensity of the cold or hot air into three to four steps, e.g., a breeze, a moderate wind and a strong wind, in an effort to optimize the room temperature of the vehicle.
The stepwise regulation of the air intensity becomes available by setting the rotation speed of the fan as an air supplying means, i.e., the rotational speed of the motor as a fan driving means, on a step-by-step basis. In this regard, a resistor is used as a means for controlling the motor.
The resistor employed for the purpose includes a radiator for radiating the heat generated when in operation, a base body for receiving step-based connector terminals and a main connector terminal, and a printed circuit board of a thin plate shape mounted within the radiator. A temperature fuse is spot-welded to an end of the printed circuit board and plays a role of a power cut-off means that disconnects electric power from the motor when a surge current flows through the printed circuit board due to the occurrence of an abnormal condition such as a failure of the motor or the like.
However, the conventional temperature fuse poses a problem in that it is highly likely to be separated from its position when subjected to an external shock. This is because the temperature fuse is merely attached to the end of the printed circuit board by spot-welding. Such problem takes place more often if the temperature fuse is attached on the top of the radiator and exposed to the outside, as is the case in recent automotive vehicles.